No abstract

Cassava (Manihot esculenta Crantz) is one of the most important root staple crops in Zambia. An estimated 30% of Zambians, over 4 million people, consume cassava as part of their daily diet. Cassava is mostly grown by subsistence farmers on fields of less than 1 ha. Cultivation of cassava is hampered by several biotic constraints, of which cassava mosaic disease (CMD) is currently the most important factor limiting cassava production in Zambia. CMD occurs in all the cassava-growing provinces and accounts for 50% to 70% of yield losses countrywide. Strategies to counter CMD were initiated in the early 1990s and included the release of CMD-resistant cassava cultivars. However, efforts to control CMD are limited because few growers plant these cultivars. More recently, to address the CMD problem, regular disease monitoring and diagnostic capabilities have been strengthened, and there is increased support for screening breeders materials. CMD is a rising threat to cassava production in Zambia. This review of CMD research on disease surveillance, CMD spread, yield losses, awareness campaigns and control options in Zambia over the past 25 years informs future control efforts and management strategies.

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22Cassava is an important food crop for most small-holder growers across sub-Saharan Africa, where production is 23 largely limited by the presence of two viral diseases: cassava mosaic disease (CMD) and cassava brown streak 24 disease (CBSD), both propagated by a vector whitefly and via human-mediated movement of infected cassava 25 stems. Despite its importance, there is limited knowledge of growers' behaviour related to planting material 26 movement, as well as growers' perception and knowledge of cassava diseases, which have major implications for 27 disease spread and control. This study was conducted to address the knowledge gaps by surveying small-holder 28 growers in Zambia. A total of 96 subsistence cassava growers across five provinces were surveyed between 2015 29 and 2017. Most growers interviewed used planting materials from their own (94%) or nearby (<10 km) fields of 30 family and friends, although some large transactions with markets, middlemen, and NGOs occurred over longer 31 distances. Information related to cassava diseases and uninfected planting material, however, only reached 48% 32 of growers. Growers with access to information were more concerned about the disease, compared to uninformed 33 growers. These data provide a basis for future planning of cassava clean seed systems to control virus diseases, 34 emphasising the critical role of grower knowledge, and consequently education, in success of these systems. In 35 particular, we highlight the importance of extension workers in this education process, as well as farmer's groups 36 and the media.